During deep geothermal resource development, the estimation of drilling efficiency and tool wear in extremely hard rocks relies primarily on CAI testing. However, the degradation of rocks caused by high-temperature water cooling conditions leads to unpredictable changes in CAI. To address this issue, this study conducted P-wave velocity, hardness, thermal conductivity testing, BTS experiments, CAI testing, and NMR testing on granite samples subjected to water cooling at different temperatures (25–600 °C). The study analyzed the degradation mechanisms of granites under high temperature-water cooling conditions, the relationship between various parameters and the CAI index, and established a dual-parameter fitting model. The results indicate that the degradation of rocks under hightemperature-water cooling conditions is primarily attributed to mineral thermal reactions, thermal expansion effects at high temperatures, and rapid cooling-induced thermal contraction effects. Once the degradation effects exceed the skeleton constraint limit, macroscopic cracks gradually form within the granite. The formation of macroscopic cracks has a mitigating effect on abrasivity. The research findings on the correlation between CAI and various parameters can provide important theoretical support for the application of high-temperature rock breaking engineering.